#24279: ORing with an empty Q() produces inconsistent results
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Reporter: ris | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: 1.7
Severity: Normal | Keywords: Q empty in or
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Using django 1.7.4, postgres 9.1.
Minimal testcase models.py:
{{{
from django.db import models
class ModelA ( models.Model ):
pass
}}}
then:
{{{
>>> for i in xrange ( 1 , 5 ):
... ModelA.objects.create ( pk = i )
>>> ModelA.objects.filter ( Q ( pk__in = () ) )
[]
}}}
correctly returning no results.
also
{{{
>>> ModelA.objects.filter ( Q ( pk__in = (1,2,) ) | Q () )
[<ModelA: 1>, <ModelA: 2>]
}}}
again, correct
however
{{{
>>> ModelA.objects.filter ( Q ( pk__in = () ) | Q () )
[<ModelA: 1>, <ModelA: 2>, <ModelA: 3>, <ModelA: 4>]
}}}
where I would have expected no instances to be returned.
The empty Q here has the effect of turning the {{{pk__in}}} into a no-op.
Interestingly, reformulating it as a (no-result-returning) subquery
produces the expected result:
{{{
>>> ModelA.objects.filter ( Q ( pk__in = ModelA.objects.filter (
pk__isnull = True ) ) | Q () )
[]
}}}
I realize that OR'ing with an empty Q may not be something you're really
supposed to do, but sometimes it does happen and this behaviour is quite
unexpected.
Apologies if this is a duplicate but I was unable to find an existing
ticket covering this.
--
Ticket URL: <https://code.djangoproject.com/ticket/24279>
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